How slow can you go?

belstone · May 31, 2016, 01:05:15 AM

My dead Gaugemaster HH feedback controller came back to life, resulting in possibly the most boring video ever uploaded to YouTube:
https://youtu.be/J-2NLbInWMQ Who says you can't get decent slow running with N gauge steam locos?

Richard

GroupC · May 31, 2016, 08:26:37 AM

I'd like the DVD version please with extras, deleted scenes and of course a director's cut.

jrb · May 31, 2016, 08:46:58 AM

Stick a DCC chip in there and they'll go even slower...

*ducks and runs for cover*

Dr Al · May 31, 2016, 09:18:39 AM

Sorry to burst the bubble, but to answer the question of the title:

To be honest, a lot slower.

A Dapol super creep, or new Farish coreless mechanisms can go way, way slower. A tidy Farish Poole 5 pole could do that too IMHO.

For example, Dapol's super creep below - admittedly a class 67, but the motor is the same as used in their steam and the gearing ratio similar - my experience is that the steam performs as well. I don't have a video of a representative steam, but can try and do one.

https://www.youtube.com/watch?v=BQuMypmVzsk

I guess this gets to the level that some will be saying: so what, that's all fine for me, why do I care? True - but if a mechanism can run reliably at such slow speeds, it'll almost certainly be very very smooth and beautiful at higher speeds, and will accelerate and slow down (with correct control of the control knob!) very very realistically and sweepingly. Also, for say a depot scene you need locos to be able to creep about at low speeds between service stages or suchlike. It adds a massive amount of realism IMHO.

Cheers,
Alan

belstone · May 31, 2016, 09:56:08 AM

Quote from: Dr Al on May 31, 2016, 09:18:39 AM
Sorry to burst the bubble, but to answer the question of the title:

To be honest, a lot slower.

A Dapol super creep, or new Farish coreless mechanisms can go way, way slower. A tidy Farish Poole 5 pole could do that too IMHO.

Yes, but those motors cost rather more than 37 pence. Both the locos in the video are slightly hamstrung by bad mechanicals - the 4F has a less than perfect driveshaft and is a bit high-geared for a goods engine on 5'3" driving wheels, and the J39 has "that" Farish tender drive. When my coreless motors turn up from China I'll put one in the 4F with a better driveshaft and drop down spur gearing. I agree with you about the value of reliable smooth slow running - that's why I am spending so much time fiddling with motors and mechanisms. No point in scratchbuilding a loco if it doesn't run properly.

Richard

Les1952 · May 31, 2016, 10:59:46 PM

Both my J39s run as slowly as that, admittedly on DCC.

Is it my imagination or is there a bit of cogging going on? The distance between the buffers of the two locos appears not to be constant as they move.

Les

belstone · June 01, 2016, 11:19:27 AM

Quote from: Les1952 on May 31, 2016, 10:59:46 PM
Both my J39s run as slowly as that, admittedly on DCC.

Is it my imagination or is there a bit of cogging going on? The distance between the buffers of the two locos appears not to be constant as they move.

Les

The 4F is right at the limit of how slowly I can get it to run - it's only a 3 pole motor, overgeared and with some stiction in the driveshaft. The J39 can be persuaded to go a little slower but then you start to get cogging even with a 5 pole. It's all down to gearing, but these two are slow enough for my needs as they are. If I could find a handheld DC controller with the kind of sophisticated motor control you get in a DCC chip I'd be a happy bunny. Some interesting stuff on here: https://tonystrains.com/dcc-motor-control-with-back-emf-and-p-i-d/

Richard

davidinyork · June 01, 2016, 06:18:09 PM

The Dapol 67s will go very slowly indeed.

belstone · June 09, 2016, 09:36:12 PM

For those people who have come back and said "that's not slow" - well, your punishment is to watch this video. J39 taking 35 seconds to cover two sleepers distance. It will go a little slower, but not 100% reliably. This speed it can maintain all day.

https://youtu.be/744eLwPWJLo

Mito · June 09, 2016, 10:06:20 PM

Got almost to the second sleeper but fell asleep.

Dr Al · June 17, 2016, 10:44:56 PM

This subject does interest me, and also rile me slightly that there is a lot of criticism levelled particularly at old mechanisms.

So for a random test, I obtained a secondhand 94xx pannier from eBay, 35 years old, 3 pole motor, brass gears, unknown history. The only thing I did was to clean the wheels and lubricate the armature bearings, and give a blast for 5 minutes either way. This is the slow running it was immediately capable of:

I consider this pretty damn good for such an old loco or unknown origin.

I also tried one of my old tool 4Fs, 5 pole Bachmann armature:

And to bring us up to date, a Dapol A4:

I struggle to see that any of these would not be good enough - the old designs really show what they are actually capable of. The new Dapol model shows extreme performance, which I doubt could really be much bettered (and why would you need to ?). To me this shows the designs old and new are pretty sound, so it's just down to QC.....

Cheers,
Alan

Dorsetmike · June 18, 2016, 10:16:34 AM

I've not got any videos but one of my best attempts was a Dapol B1 taking 5 minutes to cover 12 " , I've had good performances from Poole Farish, Fleischman, Minitrix and Union Mills as well, even had a Dapol M7 crawling.

Home made controller designed for slow running but also OK running at normal speeds.

Dr Al · June 18, 2016, 10:35:46 AM

Quote from: Dorsetmike on June 18, 2016, 10:16:34 AM
Home made controller designed for slow running but also OK running at normal speeds.

Oh - good point sir - I should have said, this was with a standard Gaugemaster W controller - nothing fancy.

Cheers,
Alan

Dorsetmike · June 18, 2016, 01:21:49 PM

I get acceptable slow running from the old Farish/AGW controllers, except for a few "jack rabbits" like Dapol M7s, for those I can switch in a series resistor to calm them down a bit.

belstone · June 18, 2016, 03:32:16 PM

Quote from: Dr Al on June 17, 2016, 10:44:56 PM
This subject does interest me, and also rile me slightly that there is a lot of criticism levelled particularly at old mechanisms.

I try to avoid being riled by model railways. It is bad for my blood pressure. I do tend to agree with you that the Poole Farish mechanisms, in good order, are much better than a lot of people would think. Most of the problems I have found have been due to dirty or badly adjusted pickups. The only reason I am messing about with remotoring them is that the Farish 5-pole, while commendably narrow, is just too long and tall for the small-boilered locomotives I have in mind for these chassis (J21 and N15).

For me it's not just a question of very slow running, but consistent speed. If you are trying to create the illusion of a hundred tons of steam loco with a model weighing maybe 30 - 40 grams, any kind of hesitation or random speed fluctuation immediately destroys that illusion. That's why I like feedback controllers and old-school motors with big heavy armatures. Coreless motors are handy because they are very small, but their main "advantages" seem otherwise to be related to efficiency - low current draw and low starting voltage. You'd have to be very worried indeed about global warming to think a motor drawing 20ma is "better" than one drawing 100ma, and low starting voltage (0.8v to get my 2MT moving) is the exact opposite of what you want in an N gauge locomotive on DC control. So I'm not overly excited by them.